51813_Sturgeon biodioversity an.PDF

lumbiaRiver(Anders^16 ).The phenomena of migra-

tory sturgeons establishing freshwater residency

upstream of dams is not understood, but it occurs

under similar circumstances with other sturgeons-

white sturgeon. A.transmontanus,in the mid-Co-

lumbia River (North et al. 1993) and lake sturgeon,

A.fulvescens,in rivers of the Great Lakes (Thuem-

ler 1985).The Connecticut and Santee/Cooper river

populations have been referred toaspartially land-

locked (Dadswell et al. 1984), but no evidence ofa

natural historical division exists.Toclarify termi-

nology, perhaps naturally landlocked populations

should be designated landlocked, and segments of

ed damlocked.

Figure 4.Relationship in nine populations between the abun-
dance of adult shortnose sturgeon and maximum upriver spawn-
ing location. The regression line represents the equation: pop- migratory populations upstream of dams designat-
ulation size = 14435 ln (river km) -50987, r^2 = 0.99, p < 0.001.

toHolyokeDam;thesefish areripe andartificially
cultured eggs develop normally (Buckley &Kynard
1981,1985b, Richmond &Kynard 1995). However,
intense netting foreggs andembryos showedthat
nofemales spawned in 1993-1994, andprobably
only 1 of 50 estimated females spawned in 1995 (P.
Vinogradov unpublisheddata). Theseresults just
belowHolyoke Damwereconcurrent in allyears
with successfulspawning and production of many
eggs andembryos by tagged females 54 km up-
streamnearTurnersFalls D a m(river km198).
Thus, the successful breeding portion of the Con-
necticutRiver population ismainly theestimated
300 or soupriver adults, of which about 25%spawn
annually(M.Kieffer&B. Kynardunpublished da-
ta). The estimated 850 lower river adults (Buckley
&Kynard^2 , Savoy&Shake^3 ) likelycontributelittle
to reproduction.Becauseonlyabout one-third of
the total Connecticut River adults are able to spawn
successfully, lowpopulation abundanceshould be
expected. Similar results of variable spawning suc-
cessamongdivided population segments of white
sturgeon,A.transmontanus,was found in the Co-
lumbiaRiver(Parsley&Beckman1994).
There isonly onenaturally landlockedsturgeon
population (e.g., resident population above a nat-
ural barrier) in the coastal rivers of North America
_the federallyendangered Kootenai Riverwhite

Biological significance of spawning location

Upstreamspawning location may be an important

component of reproductive success for shortnose

sturgeon. A comparison of nine populations across

the species’ range for the relationship between

maximum upstream spawning location and adult

abundance used the following equation:

population size=14435 ln(river km)-50987.

The regression line fits the data well (r^2 = 0.99) and

was significant (< 0.001, Figure 4). Spawning loca-

tion has a positive relationship to population size

and this relationship is best represented when

scaled with natural logs. Spawning location was

positively related to abundance in northern and

north-central populations, with only the abundance

of adults in the Connecticut and Delaware rivers lo-

cated far below the regression line. Reasons for the

low adult abundance in both these rivers were dis-

cussed previously. Recent results from the Hudson

River received after the analysis indicates the pop-

ulation has increased to 38 000 (Bain 1997 this vol-

ume). This would cause the regression line to be lo-

cated above the present position on Figure 4, but

sturgeon,whichoccursin the headwaters of theCo- (^16) Anders, P, 1993, Kootenai River white sturgeon studies.
Report to U.S. Army Corps of Engineers. Bonneville Power
Admin., Portland. 16 pp.